Spinal fusion is a surgical technique in which a spinal implant is used to join one or more vertebrae. In preparation for the spinal fusion, the one or more intervertebral discs between the vertebrae are removed. The spinal implant is surgically inserted between the vertebrae in order to maintain spine alignment and intervertebral disc height. FIG. 1, for example, illustrates a prior art spinal implant 1 inserted between adjacent first and second vertebrae 2, 3. The spinal implant can be made from various different materials, including, for example, a plastic and/or a metal (e.g., titanium). After the spinal implant is surgically inserted between the vertebrae, the vertebrae fuse with bearing surfaces defined on opposing ends of the spinal implant. The fusion process typically takes between 6 to 12 months after surgery. The post-surgery fusion process can be augmented by the placement of screws, rods, plates, and/or cages related to one or more of the vertebrae in order to stabilize the vertebrae and facilitate bone fusion.
A disadvantage of known spinal implants is that external forces can cause a movement (also known as “slippage” or “floating”) of the spinal implant relative to one or more of the vertebrae. The likelihood of such a translation is particularly high during the period between 6 to 12 months after surgery, when the fusion process typically takes place. Such movement is disadvantageous, because the positioning of the spinal implant relative to the vertebrae requires a high degree of precision in order to provide the desired therapeutic effect. Any unwanted movement can negatively impact any therapeutic and any benefit to the patient.
It is known to form a relief pattern on one or more bearing surfaces of the spinal implant in an attempt to inhibit movement of the spinal implant relative to a vertebra in a direction extending parallel and/or perpendicular to a bearing surface of the vertebra. FIG. 2, for example, illustrates a prior art spinal implant 1 having a top bearing surface 4 that defines a plurality of linear grooves and ridges 5 in the top bearing surface 4 of the prior art spinal implant 1. The grooves and ridges 5 aid in inhibiting movement of the spinal implant 1 relative to a vertebra (not shown) in a widthwise direction extending perpendicular to the grooves and ridges 5. However, the grooves and ridges 5 do not inhibit movement of the spinal implant 1 relative to a vertebra (not shown) in a lengthwise direction extending parallel to the grooves and ridges 5 or in other directions parallel to a plane defined by the top bearing surface 4. FIG. 3 illustrates another prior art spinal implant 1 having a top bearing surface 4 that defines a plurality of pyramids 6 extending therefrom. The pyramids 6 aid in inhibiting movement of the spinal implant 1 relative to a vertebra (not shown) in a lengthwise-extending direction in which opposing first and second faces 7a, 7 b of the pyramid 6 are directed, and a widthwise-extending direction in which opposing third and fourth faces 7c, 7d of the pyramid 6 are directed. However, the pyramids 6 do not inhibit movement of the spinal implant 1 relative to the vertebra in other directions parallel to a plane defined by the bearing surface 4, or in a heightwise-extending vertical direction relative to the plane.
Aspects of the present invention are directed to these and other problems.